The dig

Between demolition and rebuilding
At the beginning of the 1990s, planning law in Britain was changed so that developers were compelled to pay for the costs of investigating any archaeology on sites where they were planning to build. Since then, more than £200 million has been spent on archaeological excavations in the City of London, and our understanding of the area's Roman and other history has advanced enormously.

Time Team followed one of the biggest of these excavations, on a football pitch-sized site at Gresham Street, just north of a Roman baths and just south of the amphitheatre and fort. The excavation, carried out in phases with the archaeologists slotted in on a tight schedule between the demolition of existing buildings and the construction of new ones, took about a year from start to finish and cost the developers, Land Securities, around £1 million.

An auspicious omen
One of the very first finds made on the site, soon after digging started in December 2000, was something that the Romans would undoubtedly have regarded as auspicious – an omen of good luck. It was a tiny intaglio – an engraved green jasper gemstone from a ring, which would have been used as a personal seal on documents and correspondence. The gemstone was intricately carved with a picture of Sol, the Roman sun god, riding a four-horse chariot.

Sol was popular throughout the empire and the encouragement given to his worship by emperors from Nero onwards foreshadowed the later adoption of Christianity as the official religion of Rome. The sun god's birthday was celebrated on 25 December, which was later adopted by the Christian Church as the birthday of Jesus. The Romans would have considered the discovery of something bearing Sol's image so close to his birthday as one of the best possible omens for the dig to come. They would not have been wrong.

Key to the past
The area under excavation was one that archaeologists knew next to nothing about. Nick Bateman, project manager of the Museum of London Archaeology Service, said: 'It lies at the centre of a group of about 15 sites that we've excavated in this area around Gresham Street and in the north-west corner of the City of London over the past five or ten years. Because of its size and because it lies at the centre of these sites we hope it's going to be the key that unlocks all sorts of doors.'

For a long time, though, rather than unlocking doors the excavation seemed simply to be piling up mysteries. The archaeologists had expected that, because of its proximity to important Roman buildings such as the amphitheatre and baths, the entire site would have been heavily developed in Roman times. In fact, a large area produced no signs of any buildings at all.

The mystery of the shafts
What this area did contain was two large, timber-lined shafts, which got deeper and deeper as the excavation went on. Extensions were negotiated with the developers to enable the diggers to reach the bottom – and what they found there was extraordinary. In one shaft, they discovered a perfectly preserved Roman half-barrel, together with a dozen oak containers of at-first-sight unknown function. In the other, a number of large iron chain links, connecting bolts and split pins were recovered, all of which seemed too well-preserved to be Roman. The archaeologists even wondered whether they had fallen off a modern crane working on the site.

Even when it became clear that the finds were definitely connected with the by-now five-metre-deep shafts, it took some time to work out their function – and how the different pieces fitted together. They turned out to be parts from Roman water-lifting machines, examples of hydraulic technology as advanced as could be found anywhere in the world at the time.

Dendrochronology (tree-ring) dating revealed that one had been built around 63 AD and the other early in the second century. They were used to supply water to Roman baths.

The armless statue
Another mystery was provided by the discovery of a left hand and forearm, one and a half times life size, from a gilded bronze statue. This was found in an open drainage ditch, accompanied by hundreds of sherds from Roman amphorae (the large pottery vessels used for carrying wine, oil and other liquids), which were dated to around 70 AD. Only a dozen pieces from Roman bronze statues have ever been found in Britain; normally such valuable scrap metal would be melted down and reused. The archaeologists speculated that the statue arm would most likely have been thrown there in anger – perhaps in a revolt or after an unpopular emperor was deposed, when statues were often smashed. It might also have been placed there deliberately as an offering to the gods.

The plaster painting
The archaeology in another area of the site, sandwiched between the amphitheatre and the otherwise empty area containing the water shafts, had been badly damaged by modern development. But a few traces remained of what was once a row of Roman buildings. This yielded another unexpected find – a clump of extremely high quality, painted wall plaster. Conservator Liz Barham described it as 'the most fantastic wall plaster I've ever worked on'.

A picture of Londinium
The excavations also yielded a wealth of material that helps to fill in a picture of everyday life in Roman Londinium. A Roman kitchen, complete with hearth and pots, was uncovered as it was left following the destruction of the house in which it stood – probably in the Hadrianic Fire that devastated London in 125 AD. There were large numbers of everyday items, from coins to Roman styli (writing implements), which would last have been handled almost 2,000 years ago. And the waterlogged conditions in the shafts and other parts of the site produced a range of well-preserved organic material, including shoes and clothing accessories, that doesn't normally survive.

In combination with the other excavations that have taken place in the City of London over the past decade, the Gresham Street dig has revealed a Londinium that may have been on the edge of the Roman empire geographically but was also prosperous, sophisticated and technologically advanced. What's left of the archaeology may now be buried under 21st-century concrete, but it opened up a fresh – and frequently surprising – window onto Roman Londinium before the developers finally moved in.